1. Field of the Invention
This invention relates generally to on-board GPS sensor systems for deriving parameter values useful during the operation of moving vehicles, especially automotive vehicles traveling along roads. Such a system may derive values of parameters defining aspects of vehicle dynamics, and these values may be used in furtherance of certain warning and/or control functions.
2. Background Information
The Global Positioning System, or GPS, is a constellation of earth-orbiting satellites that continually transmit their positions in space. A known GPS receiver, or GPS sensor, is able to establish its position and velocity relative to the earth's surface by processing information obtained from GPS satellites. As a GPS sensor moves latitudinally and/or longitudinally across the earth's surface, it is capable of continually presenting its position with reference to a two-dimensional, reference frame that comprises coordinates corresponding to latitude and longitude on the earth's surface, and the sensor is also capable of presenting its velocity as a vector referenced to such a coordinate system.
It is known to place GPS sensors on automotive vehicles so that position and velocity information relative to the earth's surface is available on-board.
The value of the sideslip angle of a moving vehicle, and/or the yaw rate, can be useful in various situations involving vehicle operation. For example, such information may be an indicator of a change in road surface conditions potentially causing loss of traction. As such, sideslip-angle-related information can be a useful input to a processor in furtherance of performing warning and/or control functions.
It is known to calculate the sideslip angle of a moving vehicle from measurements of both the longitudinal velocity and the lateral velocity of the vehicle. Lateral velocity may be measured by mathematical integration of the output signal of a lateral acceleration sensor. Because sideslip angle measurements are often relatively small, increased precision of such measurements is believed beneficial. Moreover, it is believed that an ability to obtain more precise measurements with cost-effective devices could contribute toward more widespread usage of warning and/or control systems for which such information is a useful input.